Photo Credit: Brumpost

Measuring the amount of matters that makes up the whole universe can be hard. The only known fact is that almost all the universe’s matter-energy density comprises of three forces. The first is the dark energy, while the other two being dark matters, both dark and normal. The dark energy is the unrecognizable force that drives the universe far apart from within itself. The dark energy makes the universe expand sporadically.

Measuring the amount of these three forces accurately can be very challenging, but scientists declared they have done one of the most accurate measurements in order to determine the amount of matter.

According to their calculations, addition of the normal matter and the dark matter is about 31.5% of the matter-energy density of the universe, while the dark energy remaining is about 68.5%.

Astronomer Mohammed Abdullah of the university of California, Riverside and the National Research Institute of and Geophysics in Egypt said that” If all the matter in the universe were spread across space evenly, the matter would correspond to an average mass density equal to only about six hydrogen atoms per cubic meter.”
We know 80 percent of matter comprises of dark matter, most of this matter does not consist of hydrogen atoms but instead it comprises of a type of matter which cosmologists don’t understand yet. ”

A clearer understanding of the expansion rate will further improve our understanding of the Universe as a whole.

A group of scientists led by Abdullah used a procedure that is based on movement of you things around in galaxy clusters in groups of up to thousands of galaxies gravitationally joined together.

Galaxy clusters is one of the best equipments for measuring matter in the Universe, because they comprise of matter that has come together over a long period of time, which is about 13.8 billion years under gravity.

The amount of clusters we can identify in a volume of space is extremely sensitive to the number of matter, so figuring them out can give a reasonable measurement. But, counting them can be very challenging.

Abdullah said “A higher percentage of matter would result in more clusters. ”

“The goldilocks challenge for our team was to measure the number of clusters and then determine which answer was ‘just right’. But it is difficult to measure the mass of any galaxy cluster accurately because most of the matter is dark so we can’t see it with telescopes.” he added.

The researchers were able to figure out the challenge with a procedure known as GalWeight. The GalWeight is done by using the orbits of the galaxies in and around a cluster to identify which galaxies belong to any identified cluster or which does not belong with more than 98% accuracy.

According to the researchers , the GalWeight procedure provides a more accurate census of the identified cluster, this will lead to a more correct calculation.

Astronomer Anatoly Klypin of New Mexico State University explained that “A huge advantage of using our GalWeight galaxy orbit technique was that our team was able to determine a mass for each cluster individually rather than rely on more indirect, statistical methods. ”

The researchers also applied a technique to data acquired by the Sloan Digital Sky Survey, and then made a catalogue of galaxy clusters. They were then differentiated with numerical simulations of galaxies in order to figure out the amount of matter in the Universe.

The team later came up with a result which was in close agreement with the measurements of the universe’s matter-energy density. They calculated 31.5 percent matter and 68.5 percent dark energy .

“We have succeeded in making one of the most precise measurements ever made using the galaxy cluster technique,” said astronomer Gillian Wilson of UC Riverside.

“Moreover, this is the first use of the galaxy orbit technique which has obtained a value in agreement with those obtained by teams who used noncluster techniques such as cosmic microwave background anisotropies, baryon acoustic oscillations, Type Ia Supernovae or gravitational lensing.


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